What makes up the steps of the ladder in the DNA molecule?

What makes up the steps of the ladder in the DNA molecule?

DNA is made up of six smaller molecules — a five carbon sugar called deoxyribose, a phosphate molecule and four different nitrogenous bases (adenine, thymine, cytosine and guanine). The steps of the ladder are made of two bases joined together with either two or three weak hydrogen bonds.

What components make up a DNA molecule?

DNA is made of chemical building blocks called nucleotides. These building blocks are made of three parts: a phosphate group, a sugar group and one of four types of nitrogen bases. To form a strand of DNA, nucleotides are linked into chains, with the phosphate and sugar groups alternating.

What are the 5 levels of DNA structure?

Chemically speaking, DNA and RNA are very similar. Nucleic acid structure is often divided into four different levels: primary, secondary, tertiary, and quaternary.

Is DNA a tertiary structure?

Nucleic acid tertiary structure is the three-dimensional shape of a nucleic acid polymer. RNA and DNA molecules are capable of diverse functions ranging from molecular recognition to catalysis. Many more tertiary structural motifs will be revealed as new RNA and DNA molecules are structurally characterized.

What are the 3 structures of DNA?

The Building Blocks of DNA DNA has three types of chemical component: phosphate, a sugar called deoxyribose, and four nitrogenous bases—adenine, guanine, cytosine, and thymine.

What is the difference between primary and secondary structure of DNA?

Primary structure is the order in which what amino acid is bound the other with a peptide bond. This is coded for by the order of codons in a gene. Secondary structure is how the chains on amino acids interact with each other to form beta barrels and alpha helixes.

What causes DNA to bend?

The smooth overall 80° bend (90° in the central 6 bases) of the DNA is due to the additive effect of the large positive role angle of about 26° and the reduced twist of each base pair (Figure 11a). The compression of the major groove is stabilised by an extensive H-bond network and water molecules [111] (Figure 11c).

What is a DNA bending protein?

Bending proteins are involved in DNA replication, transcription, and recombination, and often participate in multicomponent complexes. Their role in these complexes is probably to fix the geometry of DNA in such complexes so that all the components will interact optimally to effect the function of that complex.

What is triple helix DNA?

A triple helix is formed after the binding of a third strand to the major groove of a duplex DNA through Hoogsteen base pairing. Pyrimidine-rich and purine-rich sequences can form stable triplex structures as a consequence of the formation of A–T–A and C+–G–C triplets (Fig. 8.5).

What is a major disadvantage to a bacterial cell of having an operon?

What is a major disadvantage to a bacterial cell of having an operon? If there is a mutation in a regulatory region, none of the proteins will be synthesized.

Is lac operon positive or negative?

The lac operon is a negatively controlled inducible operon, where the inducer molecule is allolactose. In negative repressible operons, transcription of the operon normally takes place. Repressor proteins are produced by a regulator gene, but they are unable to bind to the operator in their normal conformation.

How does the lac operon work?

The lac operon of E. coli contains genes involved in lactose metabolism. It’s expressed only when lactose is present and glucose is absent. Two regulators turn the operon “on” and “off” in response to lactose and glucose levels: the lac repressor and catabolite activator protein (CAP).

Why is the lac operon important?

The classic example of prokaryotic gene regulation is that of the lac operon. This operon is a genetic unit that produces the enzymes necessary for the digestion of lactose (Fig. 16-13). The lac operon consists of three contiguous structural genes that are transcribed as continuous mRNA by RNA polymerase.

Where is the lac operon found?

E. coli

What turns the lac operon off?

An operon is a group of genes that are regulated together. When lactose is not present, the DNA-binding protein called ► lac repressor binds to a region called the operator, which switches the lac operon off. When lactose binds to the repressor, it causes the repressor to fall off the operator, turning ► the operon on.

Is lac operon present in humans?

Operons are common in bacteria, but they are rare in eukaryotes such as humans. In general, an operon will contain genes that function in the same process. For instance, a well-studied operon called the lac operon contains genes that encode proteins involved in uptake and metabolism of a particular sugar, lactose.

What is lac operon system?

The lactose operon (lac operon) is an operon required for the transport and metabolism of lactose in E. coli and many other enteric bacteria. The gene product of lacZ is β-galactosidase which cleaves lactose, a disaccharide, into glucose and galactose.

What are the three important features of the lac operon?

The lac operon consists of three structural genes: lacZ, which codes for β-galactosidase, which acts to cleave lactose into galactose and glucose; lacY, which codes for lac permease, which is a transmembrane protein necessary for lactose uptake; and lacA, which codes for a transacetylase that transfers an acetyl group …

What is operon concept?

Operon Theory is the concept of gene regulation proposed by François Jacob and Jacques Monod (1961). An operon is a group of structural genes whose expression is coordinated by an operator. The repressor encoded by a regulatory gene binds to the operator and represses the transcription of operon.

What are the types of operon?

Operons are of two types, inducible and repressible.

What is the structure of an operon?

Operon Structure Operons are regions of DNA that contain clusters of related genes. They are made up of a promoter region, an operator, and multiple related genes. The operator can be located either within the promoter or between the promoter and the genes.

What are the four parts of an operon?

An operon consists of an operator, promoter, regulator, and structural genes. The regulator gene codes for a repressor protein that binds to the operator, obstructing the promoter (thus, transcription) of the structural genes. The regulator does not have to be adjacent to other genes in the operon.

What is meant by Cistron?

A segment of DNA that contains all the information necessary for the production of a single polypeptide and includes both the structural (coding) sequences and regulatory sequences (transcription start and stop signals). ( see also monocistronic mRNA; operon; polycistronic mRNA)

What is the function of operon?

Operon, genetic regulatory system found in bacteria and their viruses in which genes coding for functionally related proteins are clustered along the DNA. This feature allows protein synthesis to be controlled coordinately in response to the needs of the cell.

Why are there no operons in eukaryotes?

When an operon is transcribed, all of the genes on the operon are on the same mRNA. Operons occur in prokaryotes, but not eukaryotes. In eukaryotes, each gene is made on individual mRNAs and each gene has its own promoter. Cells can’t afford to waste energy making genes if they don’t need them.

Do plants have operons?

Operons (clusters of co-regulated genes with related functions) are a well-known feature of prokaryotic genomes. Functional gene clustering also occurs in eukaryotes, from yeasts to filamentous fungi, mammals, nematodes, and plants [2].

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